Third extinction event

The Permian - Triassic extinction event was 251.9 million years ago.

At earth’s most severe extinction temperature spiralled out of control. First it dropped down and then a chain reaction kick-started rapidly pushed up to a global average temperature to 32°C. It wiped out almost all the animal and plant species on the planet, within a very short space of time.

At the start of third mass extinction millions of cubic miles of magma built up beneath the Siberian crust. And then, the Earth erupted, spewing out vast amounts of lava flooding the area under a sea of molten rock, called the Siberian traps. It's a type of volcanic eruption called a flood basalt. The Siberian flood basalt released enough lava to cover an area the size of the United States under one mile of molten rock.
Volcanoes produce lava, ash and gas. Lava goes a relatively short distance. The ash will go further, flying through the air. But the real killer was the release of billions of tons of sulphur dioxide (SO2) into Earth's atmosphere. First it turned into acid rain and bleached vast areas of the Earth. Then it created volcanic winters which sent global temperatures plummeting. Around the world the climate change killed plants and the food chain fell apart and 10 % of species perished. Also carbon dioxide (CO2) was released in Earth's atmosphere and became 20 times higher than at the beginning of the industrial revolution. The result was a rise in global temperature of at least 5°C. After 50,000 years of the start of the Siberian eruptions the oceans oxygen level dropped to the point where there's no oxygen left due to a temperature increase of Earth's oceans by 5°C, Then organisms that can't stand oxygen thrived and produced hydrogen sulphide (H2S). Because it is poisonous to oxygen breathing life it became the death of virtually all life in the sea. The temperature rise of the oceans also thawed the frozen methane hydrate at the bottom of the oceans. The released methane transformed into billions of tons carbon dioxide before this entered the Earth's atmosphere. The temperature went up another 5°C. The world was now 10°C hotter, unable to adapt to the extreme and rapid climate change, 95 % of all life ceased to exist.

Extinction rates:

• 96% species
• 56% genera
• 57% families

Before the third extinction the Earth slowly warmed to warm and dry conditions. The ecosystem was a fully developed and stable. Huge herds of cow sized herbivores grazed on the plains. But this flourishing world was also home to the Earth's most efficient carnivore. Armed with serrated interlocking teeth, this ferocious animal was the ancient world's top predator over 150 million years before T-Rex came along.
In these climate conditions, tribal mammals evolved. These ancestors of mammals adapted by having a nasal bridge that warmed and moistened the incoming air. They may also not have been as cold-blooded as earlier species and adapted by laying eggs with a protected shell that prevents dehydration.
Some of the small plant eating creatures were digging burrows for shelter. And it's very likely that it was one of the reasons why it was able to survive the mass extinction, One of the this species line became a mammal after the extinction.